OBJECTIVETo explore the potential effects of berberine on influenza virus infection both in vitro and in vivo.

METHODSIn vitro anti-influenza virus assays were performed by cytopathogenic effect and neuraminidase assays in Madin Darby canine kidney cells. In vivo anti-influenza virus assays were performed on the viral pneumonia model of mice. The numbers of mice that died within day 2 to day 14 postinfection were recorded to calculate the mortality. On days 2, 4, and 6, the viral titers in the lungs were determined by hemagglutination assay; hematoxylin/eosin staining was used to assess the pathogenic changes of lung tissues; the concentrations of tumor necrosis factor-alpha (TNF-α) and monocyte specific chemoattractant molecule (MCP-1) were measured by radio immunoassay or enzyme-linked immunosorbent assay; the concentrations of nitric oxide (NO) and inducible nitric oxide synthetase (iNOS) were detected by colorimetric method; reverse transcription polymerase chain reaction was used to detect the mRNA level of TNF-α and MCP-1.

RESULTSBerberine showed inhibitory effects on cytopathogenic effects and neuraminidase activity of virus, with the therapeutic index 9.69. In vivo, berberine decreased mice mortality from 90% to 55%, reduced virus titers in the lungs on day 2 postinfection (P<0.05). The lung histology scores were 1.50 ± 0.67, 4.50 ± 1.00, and 5.50 ± 1.00 in the berberine group on days 2, 4, and 6, respectively, which were significantly reduced compared to 2.17 ± 0.22, 6.83 ± 0.44, and 8.50 ± 0.33 in the infected group (P<0.05). The productions of NO and iNOS were repressed by berberine compared with those in the infected group (P<0.01). The transcription and expression of TNF-α were inhibited by berberine on day 4 (P<0.01) and day 6 (P<0.05), and those of MCP-1 were inhibited on day 6 (P<0.01) compared with the infected group.

CONCLUSIONSBerberine exhibited antiviral effects on the influenza virus both in vitro and in vivo. The possible therapeutic mechanism of berberine on influenza-induced viral pneumonia might be inhibiting the virus infection, as well as improving the pathogenic changes by repressing inflammatory substances release.